Conventionally, an industrial robot has been widely utilized for carrying out an object to be conveyed from a storage part where the object to be conveyed is accommodated and for carrying an object to be conveyed into the storage part. As this type of an industrial robot, a substrate conveying robot has been known which carries out a substrate such as a semiconductor wafer that is an object to be conveyed from a vacuum chamber as a storage part and which carries a substrate into the vacuum chamber (see, for example, Patent References 1 and 2).
The substrate conveying robot which is described in the Patent Reference 1 includes a first arm which is formed in a substantially “L”-shape and whose vertex portion is turnably held by a drive box in which a drive part is disposed, a second arm and a third arm whose one end sides are respectively turnably held at both ends of the first arm, and substrate holding parts (hand) which are turnably held at the other end sides of the second arm and the third arm.
The substrate conveying robot is provided with three motors for individually driving the first through the third arms. The first through the third arms are turned with respect to the drive box in a state where a turning center of a hand for the second arm and a turning center of a hand for the third arm are superposed each other. Therefore, the substrate conveying robot is capable of decreasing its turning diameter. The substrate conveying robot is structured so that only one piece of substrate is mounted on one hand, and only one piece of substrate is conveyed by a single carrying-in operation or a single carrying-out operation.
Further, a substrate conveying robot described in Patent Reference 2 is structured roughly similar to the substrate conveying robot described in Patent Reference 1.
[Patent Reference 1] Japanese Patent Laid-Open No. Hei 10-163296
[Patent Reference 2] Japanese Patent Laid-Open No. Hei 7-171778
In recent years, in order to improve productivity, an industrial robot has been required to convey a plurality of substrates by a single carrying-in operation or carrying-out operation. However, the substrate conveying robot described in Patent Reference 1 or 2 is structured so that only one piece of substrate is conveyed by a single carrying-in operation or carrying-out operation. In other words, Patent Reference 1 or 2 does not disclose a specific structure of an industrial robot which is capable of conveying a plurality of substrates by a single carrying-in operation or carrying-out operation while decreasing its turning diameter.